Coded signaling apparatus



Feb. 7, 1950 c. E. STAPLES comma SIGNALING APPARATUS 3 Sheets-Sheet 1 Filed June 14., 1946 M5 Awroavm Feb. 7 1950 c. E. STAPLES CODED SIGNALING APPARATUS 3 Sheets-Sheet 2 Filed June 14, 1946 KTIUAMW I INVENTOR HIS : WMEQ r-iliLiil. l Lo C- E. STAPLES CODED SIGNALING APPARATUS Feb. 7, 1950 5 Sheets-Sheet 3 Filed June 14', 1946 INVENTOR.

#WQUQVW Patented Feb. 7, 1950 CODED SIGNALING APPARATUS Crawford E. Staples, Pittlbi n'gh, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application June 14, 1946, Serial N0. 676,643

Claims.

My invention relates to coded track circuit railway signaling systems and particularly to means for generating impulses of coded energy for use in systems of this type.

In an application for Letters Patent of the United States, Serial No. 674,436 of Henry 8. Young, filed June 5, 1946, for Railway signaling systems, there is shown a system of coded track circuit signaling for single track stretches. That system is arranged so that normally impulses of energy are transmitted alternately in opposite directions over the rails of the single track stretch from end to end to operate code following relays at the ends of the stretch and thus energize code detecting relays to permit the head block signals to be cleared and authorize traffic to enter the stretch.

An object of this invention is to provide improved code generating means which is adapted for use in a signaling system of the type described and which operates so that the impulses of energy supplied thereby are of a predetermined duration which is adequate to insure that even though the track stretch is divided into several track sections, an impulse of energy supplied to an end of the stretch will be repeated by front contact coding cut-section apparatus through all of the sections in the stretch.

A further object of the invention is to provide improved code generating means of the type described which is arranged so that it is ineffective to supply energy to the rails of the stretch or to interrupt the connection of the associated track relay with the rails of the stretch while the track relay is energized.

Another object of the invention is to provide improved code generating equipment of the type described which is governed by a codetransmitter of standard construction so that the code impulses supplied by the equipment are of substantially uniform, accurately measured length regardless of variations in operating conditions.

A further object of the invention is to provide improved code generating means of the type described which is arranged so that the length of the energy impulses supplied thereby is unaffected by variations in the time in the cycleof operation of the code transmitter at which release of the track relay occurs.

Another object of the invention is to provide improved code generating means of the type described which operates so that the interval between impulses of energy is substantially longer than the energy impulses.

improved code generating means of the type described which operates so that the track rails are short-circuited for an interval between the time at which the supply of energy to the track rails is interrupted and the time at which the track relay is connected across the track rails.

Another object of the invention is to provide improved code generating means adapted for use at the opposite ends of a single track stretch and arranged so that the equipment at each end of the stretch operates to supply an impulse of energy following release of the associated track relay to thereby cause impulses of energy to be transmitted alternately in opposite directions over the rails of the track stretch.

A further object of the invention is to provide improved code generating means of the type described which operates so that the duration and frequency of the energy impulses supplied over the rails of the stretch in both directions are such that energy is supplied to the rails of a section in the stretch for less than one-half of the time to thereby limit the charge developed in the track ballast to a value which will not interfere with operation of the track relays.

Another object of the invention is to provide improved code generating means of the type'described which is arranged so that when the stretch is occupied the equipment at each end continues to supply locally generated impulses of energy to the stretch and so that energy impulses supplied to the opposite ends of a stretch occur at different frequencies to thereby insure that when the stretch is vacated, the coordinated P operation of the equipment at opposite ends of the stretch will be resumed promptly with the result that the code detecting means at both ends of the stretch will quickly show that the stretch has been vacated. 6

A further object of the invention is to provide improved code generating means of the type dedescription taken in connection with the accom- A further object of the invention is to provide ll panying drawings.

I shall describe one form of code generating means embodying my invention together with one modification which I may employ, and shall then point out the novel features thereof in claims.

In practicing my invention I provide at each end of a single track stretch a continuously operating code transmitter which controls three result that they complete a. cycle of operation including six distinct steps once during every three cycles of operation of the code transmitter. During one of the six steps in a cycle oi. operation of the transmitter relays the track battery 'is connected across the track rails to supply an impulse of energy the duration of which is determined by the code transmitter so that the impulse will always be of accurately measured length. Where polarized track circuit energy is employed, the circuits governed by the transmitter relays are arranged so that the track rails are short-circuited during the step immediately following the supply of energy to the track rails. The circuits governed by the transmitter relays are also arranged so that the track relay is connected" across the track rails during all steps .in the cycle of operation of the transmitter relays except the step during which energy is supplied to the track rails and the step during which the track rails are short-circuited.

The energy for operating the transmitter relays is supplied over a circuit which includes a back contact of the track relay so the transmitter relays cannot operate when the track relay is picked up. This provides protection agains improper coding operation of the track relay in the event that foreign current is present, while it results in release of the transmitter relays when the track relay picks up so that on subsequent release of the track relay a new cycle of operation of the transmitter relays is initiated and thereafter an impulse of energy is promptly supplied to the track rails. Accordingly, the equipment at each end of the stretch operates to supply an impulse of energy to the stretch in response to receipt of an energy impulse from the other end of the stretch.

In the drawings, Figs. 1A and 18 when placed together with Fig. 1B at the right are a diagram of a stretch of track equipped with signaling apparatus employing the code generating means provided by this invention, and

Fig. 2 is a diagram showing a modified form of equipment which may be employed where the energy supplied to the track 'rails is always of the same polarity.

Similar reference characters refer to similar parts in each of the several views.

Referring to the drawings there is shown in Figs. 1A and 13 a stretch of single track railway through which traffic may move in either direction between passing sidings I and II. The track rails l and 2 of the track stretch are divided by insulated joints into a plurality of track sections, each of which is provided with two coded track circuits, one for each direction of trafllc. As shown, the single track stretch is divided into three track sections, but it should be understood that this invention is not restricted to this exact arrangement and that the single track stretch may be divided into a larger or a smaller number of track sections as may be required.

Each end of the single track stretch is equipped with code generating means provided by this invention for controlling the supply of impulses of energy to the rails of the track stretch, and for also controlling the connection of the associated track relay with the track rails.

As this invention is directed primarily to the construction and operation of the code generating means, only as much of the remainder of the signaling system has been illustrated as is essential to the understanding of the code generating means, and it is to be understood that 5 the signaling apparatus may be arranged as shown in the above-identified application of Henry S. Young. Y

In order that the relationship of the equipment shown in this application and that employed in the system shown in the application of Henry S. Young may be readily understood, the reference characters which are employed in that application have been employed to designate corresponding elements in this application.

A head block signal is located at each end of the single track stretch and controls entrance of trafllc into the track stretch, while these signals are governed by the associated code following track relays which are operated by coded energy supplied over the rails of the stretch. Each of the head block signals is capable of displaying a red or stop indication, and a green or clear indication.

At each end of each passing siding there is an entering signal which governs entrance of traflic into the main track portion beside the siding. Each oi the entering signals is governed by trafiic conditions in the main track section beside the associated siding and in the single track; stretch beyond the siding so as to display a stop, caution or clear indication. The means for controlling the entering signals is not essential to an understanding of this inven-. tion, and has notbeen shown in this application in order to simplify this disclosure. However, it is assumed that the entering signals are normally at stop and are approach controlled, as shown in the application of Henry S. Young, so as to display an appropriate indication on 0 the approach 01' atrain. As shown in the drawings, contacts governed by the signal mechanisms control the supply of energy to relays DPR and HPR which repeat the clear and caution indications, respectively.

The head block and entering'signals, as shown, are of the searchlight type shown in Letters Patent of the United States No. 1,864,224, issued June 21, 1932, to Wesley B. Wells for Light signals, but it should be understood that any form of wayside 50 signals may be employed.

Trafllc in the single track stretch approaching the entering signals may be controlled by distant signals which may be governed by the coded energy transmitted over the end track sections in the single track stretch. Since the manner of controlling these distant signals is not essential to an understanding of this invention, these sig-. nals and the control circuits therefor have been omitted from this application, but it should be so understood that these signals may be controlled as shown in the above-identified application of Henry S. Young.

Each signal location is provided with a suitable source of direct current, such as a battery, not

shown, the terminals of which are designated 8 and C in the drawings.

The equipment is shown in the condition which it assumes when the single track stretch and the main track portions beside the passing sidings are vacant and when the hand-throw switches IW and 2W at the ends of the single track stretch are in their normal position in which they connect the single track stretch with the main track portions beside the passing sidings.

As the main track portions beside the passing -verse polarity.

Construction and operation of code generating equipment at left-hand end of single track stretch The supply of energy from track battery 2TB to the rails of section 23T, and the connection of track relay 2TB across the rails of section 2-3T, are governed by the code generating means provided by this invention. As shown, this means comprises the code transmitter 2CT and the associated transmitter relays 2CRA,

ICRB and ZCRC.

The code transmitter 2CT, as well as the other code transmitters employed in this system, is preferably of a type which operates at a relatively low speed, such as at the rate of '75 code cycles per minute, so that the code transmitter contacts occupy each of their two positions for a relatively long period, such as .4 of a second.

The code transmitter ZCT and the transmitter relays ZCRA, 2CRB and ZCRC cooperate as hereinafter explained in detail to supply impulses of energy to the rails of the track stretch and to connect the track relay ZTR across the track rails. These transmitter relays together with the code transmitter provide means for supplying to the rails of the stretch impulses of energy of accurately measured length which are long enough to be certain to be repeated through the single track stretch to the other end. In addition, these relays and the code transmitter provide means for insuring that the time interval be- "2cm in series, mint contact "of relay term, and back contact 20 of relay IDPR to track tall I, while the negative terminal of the battery is connected over back contact 2| of relay IDPR to track rail 2. v I

The circuit of the track relay 2TB. is open at back contacts i6 and H of relays ICRB and ICRA so the track relay is released and its back contact 28 is closed. v a

As shown, the relays ZCRA and ICRB are energized by current supplied over their stick circuits. The stick circuit for relay 2CRA is traced from terminal B over contact 23 which is governed in accordance with the position of switch IW so as to be closed when and only when this switch occupies its normal position, front contact 25 of track relay ITR for the sidin section IT, back contact 2G'of track relay 2TB, back contact 21 of relay ZCRC, and front contact 28 oi relay ICRA. The stick circuit for relay 20KB is traced from contact 26 of relay ZTR over front contact 29 of relay 2CRA, and its own front contact 30.

As hereinafter explained in detail, the transmitter relays 2CRA, ZCRB and ICRC operate cyclically in response to operation of the code transmitter 2CT so as to complete one cycle of operation every three cycles of operation of the code transmitter, unless operation of the relays ZCRA, ZCRB and ZCRC is altered because of picking up of the track relay 2TR. The cycle of operation .of the transmitter relays ZCRA, ZCRB and 2CRC is such that these relays are first successively picked up, and are then successively released so there are six steps in the complete cycle, one step for each movement of the contacts of the code transmitter.

The position of the contacts of the transmitter relays 2CRA, ZCRB and ZCRC, and of the code transmitter 2CT, during each of the six steps in the complete cycle is shown by the following chart in which the first stepin the cycle is assumed to be the condition in which the contacts of the relays 2CRA, 2CRB and ZCRC,

tween successive energy impulses supplied to the and of the code transmitter 2CT are all released.

CT Step ZCRA ZCRB 1 20110 i Down.. 1 Down Down Down. Track Relay Connected Across Track Rails. Up 2 Up .do ..do. Do. 'Down 3 do Up do. Track Battery Connected Across Track Rails. 1) 4 do ...do- Up Rails Short-Circuited. Down 6 Down... .-.do--. -do Track Relay Connected Across Track Rails. Up 6 do Down ..do Do.

left-hand end of the single track stretch is long enough to enable impulses of energy supplied at the other end of the stretch to be transmitted over the rails of the stretch to pick up the track relay 2'IR. I

As hereinafter explained, the transmitter relays SCRA, SCRB and SCRC and the code transmitter 5CT at the other end of the single track stretch cooperate in a similar manner to supply energy impulses to the track rails and to connect the track relay 5TB. across the track rails.

The code transmitter 2CT and the associated transmitter relays are shown in the condition which they assume when energy is being supplied from track battery 2TB to the rails of section 2-3T. At this time the positive terminal of the battery is connected over back contacts H and I! of relay 2CRC in multiple, front contact ii of As shown in Fig. 1A of the drawings, the relays ICRA, ICRB and ZCRC and the code transmitter 2C'I are in the condition designated step 3 in the chart above.

On the next movement of the contacts of the code transmitter 2CT to their picked-up position energy is supplied to relay ZCRC over the circuit which is traced from contact 26 of relay 2TB over front contact 34 of relay ZCRB, and front contact 35 of code transmitter ZCT, and when relay 2CRC picks up, its contact 36 establishes a stick circuit including front contact 34 of relay 2CRB. In addition, when relay ICRC picks up, its contact 21 establishes a stick circuit which includes front contact 38 of code transmitter 281'.

When code transmitter ZCT picks up to begin step 4, energy is also supplied over its front relay ICRB, front contacts I! and II of relay" contact 39 to relay ICRA over the circuit which includes front contact 20 of relay ICRA, while relay 2CRB is maintained energized by current supplied over the circuit which istraced from contact 26 of track relay ITR over front contact 29 of relay 20M and its own front contact 30. The energy supplied to relay 2CRA over its own front contact 23 and front contact 33 of code transmitter 2CT keeps the contacts of relay 2CRA picked up after interruption of the supply of energy thereto over back contact 21 of relay ZCRC, and over front contact 3| of code transmitter 201. The equipment is now in the condition designated step 4 in the chart above.

When relay ICRC picks up, its contacts I4 and I5 interrupt the circuit traced above for supplying energy from track battery 2TB to the track rails and short-circuit the track rails over the circuit which is traced from track rail 2 over back contact 2| of relay IDPR, front contacts l4 and I5 of relay ICRC in multiple, front contact iii of relay ZCRB, front contacts I! and I8 of relay ZCRA in series, front contact I9 of relay 2CRB, and back contact 20 of relay IDPR to track rail i. This short-circuiting of the track rails dissipates any energy stored in the track circuit as a result of previous supply of energy to the track circuit from the track battery. and eliminates the possibility of operation of the track relay 2TR by stored energy from the track circuit on subsequent connection of the track relay with the track rails.

On the next movement of the contacts of code transmitter ZCT to their released position, contact 39 interrupts the circuit traced above for energizing relay ZCRA and after a short time interval relay 2CRA releases. At this time relay 2CRB is maintained energized over the circuit which is traced from back contact 26 of relay 2TB. over front contact 34 of relay ZCRB, and back contact 35 of code transmitter 201, so the contacts of relay 2CRB remain picked up. As relay ZCRB is picked up, energy is supplied to relay ZCRC over the circuit which is traced from contact 26 of relay 2TB over front contact 34 of relay ZCRB and front contact 3i of relay ZCRC so the relay 2CRC remains picked up. The equipment is now in the condition designated step 5 in the chart above.

On release of relay ZC'RA its contacts I1 and i8 interrupt the circuit traced above for shortcircuiting the track rails i and 2, while the track relay ZTR is now connected across the track rails over the circuit which is traced from track rail 2 over back contacts I. and ll of relay ICRA in series, and winding of relay 2TB, to track rail I. Accordingly, whenever relay 2CRA is released, the relay ZTR. is connected across the track rails and may respond to energy supplied over the track rails from the other end of the track section even though relays ICRB and ICRC are both picked up.

During the next picked-up period oi the contacts of the code transmitter ICT its contacts 35 and 39 interrupt the circuits for supplying energy to relay ICRB and its contacts release. At this time, energy is supplied to relay ICRC over the circuit which is traced from back contact 26 of relay ITR. over front contact 21 of relay ZCRC and front contact 38 of code transmitter 2CT. Accordingly, during this picked-up period of the code transmitter 2CT the relay ICRC remains energized and its back contact 21 interrupts the circuit including front contact 3| of code transmitter 201 for supplying energy to relay 2CRA and relay 20M is not picked up during this picked-up period of the code transmitter. As relay ZCRA remains released it contacts I! and it continue to connect track relay 2'I'R. across the track rails. The equipment is now in the condition designated step 3 in the chart above.

During the next released period of the contacts of code transmitter 2CT, its contacts 3! and II interrupt the circuits for supplying energy to relay ICRC and it releases so that its contacts 21 and 36 additionally interrupt the relay stick circuit, while back contact 21 of relay ICRC is closed. The equipment is now in the condition designated step I in the chart above.

During the next picked-up period of the contacts of the code transmitter 2CT energy is sup plied to the relay 2CRA over the circuit which is traced from contact 26 of track relay 2TB, back contact 21 of relay ICRC, and front contact 3| of code transmitter ICT. The energy supplied to relay 2CRA picks up the relay contacts so that contact 2. establishes one of the relay stick circuits to keep the relay energized after movement of the contacts of code transmitter ZCT to their released position. The equipment is now in the condition designated step 2 in the chart above.

When relay ZCRA picks up, its contacts I! and I8 interrupt one circuit for connecting track relay 2TR across the track rails and establish a circuit including back contacts [6 and is of relay ZCRB for connecting the track relay 2TB across the track rails.

During the next movement of the contacts of code transmitter ZCT to their released position, energy is supplied to the relay ZCRB over the circuit which is traced from contact 26 of track relay 2TB, over front contact 29 of relay ICRA and back contact 39 of code transmitter 2CT and the contacts of relay ZCRB pick up. When relay 2CRB picks up, its contact 3!! establishes one stick circuit for the relay while its contact 34 establishes another stick circuit for the relay, and the equipment is again in the condition designated step 3 in the chart above.

In addition, when relay ICRB picks up, its contacts I6 and I9 interrupt the circuit for connecting track relay 2TB. across the track rails and establish the circuit traced above for connecting the track battery 2TB across the track rails, and the equipment is now in the condition in which it is illustrated in Fig. 1A of the drawings.

From the foregoing it will be seen that as a result of operation of the contacts of the code transmitter ICT between their two positions the relays 2CRA, ICRB and ICRC are picked up on successive operations of the code transmitter contacts, while on continued operation of the code transmitter 2CT the relays ICRA, ZCRB and 2CRC are released on successive operations of the code transmitter contacts, whereupon the cycle of operations just described is repeated.

As one relay is picked up in response to each movement of the contacts of the code transmit ter, and as one relay is thereafter released in response to each movement of the contacts of the code transmitter, the complete chain of operation of these relays occurs in six operations of the contacts of the code transmitter, that is,

in three code cycles.

step in the cycle immediately following the sup-.

, mimih m...

ply of energy to the track rails (step 4), the relay ICRC picks up to discontinue the supply of energy to the track rails and to short-circuit the rails and thereby dissipate any energy stored in the track circuit and to also provide a circuit for the flow of energy inductively discharged from the track circuit on interruption of the supply of energy thereto from the track battery. During the remaining four out of the six periods or steps in the chain of operation of the relays 2CRA, ZCRB and ZCRC, the track relay 2TB, is connected across the track rails so that it may respond to energy supplied over the rails of the stretch.

As is clearly shown in Fi 1A of the drawings the energy which is supplied to the pick-up and stick circuits for the transmitter relays 2CRA, ZCRB and 2CRC is supplied over the circuit which includes back contact '26 of the track relay 2TB. so that when the track relay 2TH. picks up the supply of energy to the relays ZCRA, 2CRB and 2CRC is cut oil. As is also clearly shown in the drawings, the circuit of the code transmitter ZCT is independent of the track relay ZTR and the code transmitter operates continuously irrespective of operation of the track relay. Each of the transmitter relays ZCRA, ZCRB and ZCRC is snubbed by a rectifier which delays release of the relay contacts long enough to bridge momentary interruptions in the supply of energy to the relay winding, such as occurs during movement of the contacts of the code transmitter between their two positions. However, the rectifiers will not delay release of the relays long enough to bridge a sustained interruption in the supply of energy to the winding of a relay, as occurs when the track relay picks up. Accordingly, when the track relay ZTR picks up, and its contact 26 interrupts the circuits of the relays ZCRA, ZCRB and ZCRC, any of these relays which are picked up will release and all of these relays thereafter remain released until picked up as a result of operation of code transmitter 201 subsequent to release of the track relay.

If picking up of the track relay 2'I'R results in release of relay ZCRA, the circuit of the track relay will be interrupted during movement of the contacts of relay ZCRA between their picked-up and released positions. However, this interval is so short that the contacts of relay ZTR remain picked up.

As previously explained, energy is supplied from battery 2TB to the track rails in the step or period in which relays ZCRA and 2CRB are picked up and relay ZCRC is released, while, during the next or succeeding step or period, the relay ZCRC is picked up and the track rails-are short-circuited. During these two periods the track relay 2TB is not connected across the track rails, and hence cannot be picked up, so its contact 26 is certain to remain released and maintain the circuit for supplying energy to the relays 2CRA, ZCRB and 2CRC, and there is no possibility that the supply of energy from the track battery to the section rails, or the short-circuiting of the track rails, will be interrupted or disturbed by picking up of the track relay. During the remaining four steps or periods in the chain of relay operation, that is, when (1) relay ZCRA is released and relays ZCRB and ZCRC are picked up; (2) relays ICRA and ZCRB are released and relay 2CRC is picked up; (3) relays 2CRA, 2CRB and 2CRC are released; or (4) relay 2CRA is picked up and relays ZCRB and.

ICRC are released, the track relay ZTR is con- 10 nected across the section rails and may respond to energy supplied over the track rails.

As will be explained below, a short period will elapse from the time at which an impulse of energyis supplied to the single track stretch at the left-hand or west end of the stretch, and the time at which an impulse of energy supplied to the right-hand oreast end of the stretch is received over the track rails at the west end of the stretch. This period of time will ordinarily be longer than the time during which the track rails are short-circuited at the west end following the disconnection of the track battery from the track rails so the track relay will not ordinarily pick up immediately after it is connected across the track rails.

However, when the trackrelay picks up, any of the relays 2CRA, 2CRB and 2CRC which are picked up will release and remain released as long as, the track relay is picked up. If, at the time the track relay releases, the contacts of the code transmitter are in their released position, the relays ZCRA, ZCRB and ZCRC remain released until the code transmitter contacts pick up. When the track relay is released and the code transmitter contacts are picked up, energy is supplied to the relay ZCRA and its contacts pick up so.

that on subsequent movement of the contacts of code transmitter 2CT to their released position energy is supplied to relay 2CRB and its contacts pick up to interrupt the circuit of the track relay and to establish the circuit for supplying energy from the track battery to' the track rails.

From the foregoing it will be seen that if the track relay is not operated by energy received over the track rails, the code transmitter 2CT and the associated transmitter relays cause an impulse of energy to be supplied to the track rails once during every six steps or periods in the chain of relay operations, or during one-half of every third cycle of the code transmitter.

However, if the sequence of operation of the transmitter relays 2CRA, '2CRB and ZCRC is interrupted by picking up of the track relay 2TB, an impulse of energy is supplied to the track rails during the first released period of the contacts of the code transmitter following the first pickedthe track relay contact.

Accordingly, during the times in which the track relay ZTR is responding to coded energy the sequence of operation of the transmitter relays ZCRA, 2CRB and ZCRC may be interrupted so these relays do not cause energy to be supplied to the track rails once during every three cycles or six periods in the operation of the contacts of the code transmitter, but during a period in the operation of the contacts of the code transmitter which is determined by the release of the track relay.

As will be seen from the chart above, the track relay 2TB is connected across the track rails at the start of the fifth period in the cycle of operation of the'code transmitter so the track relay contacts may pick up at this time, thereby releasing the relays ZCRB and 2CRC and when the track relay releases, initiating a new cycle of operation of relays ZCRA, ICRB and ZCRC.

Under some conditions, if the track relay 2TB. does pick up, it will release prior to or during the period corresponding to the sixthperiod in the previous cycle of operation of the relays ZCRA, ZCRB and ZCRC. During the sixth period the contacts of the code transmitter 2CT are picked up and if the track relay releases during 11 this period in the cycle of operation of the code transmitter, the relay 2CRA will pick up immediately. If this occurs, relay 2CRB will be picked up during the next period in the cycle of operation of the code transmitter 2CT, and energy is supplied to the track rails from the track battery during this period, which occurs at the time at which the first step in a new cycle would take place if the previous cycle had not been terminated by picking up of the track relay.

On the other hand the track relay 2TB. may not pick up until the time corresponding to the second period in a new cycle of operation of the relays ZCRA, ZCRB and ZCRC, at which time relay ZCRA is picked up and relays ZCRB and ICRC are released. As picking up of the track relay results in release of relay ZCRA, the relay ICRB will not be picked up during the next period in the operation of the code transmitter contacts so energy will not be supplied to the track rails at this time.

The energy impulses supplied over the track rails to the track relay ZTR are of such duration that the track relay, if picked up during the time corresponding to the second period in a new cycle, will release during the next succeeding period in the cycle, which corresponds to the third period in the new cycle. Accordingly, during the time corresponding to the following or fourth period of the new cycle of operation, energy will be supplied to the relay 2CRA so that during the time corresponding to the next or fifth period in the new cycle of operation of the relays ZCRA, ZCRB and 2CRC energy is supplied to relay 2CRB and it picks up to cause energy to be supplied from the track battery to the track rails. Under these conditions, therefore, the supply of energy to the track rails occurs after four cycles of operation of the code transmitter.

From the foregoing it will be seen that the equipment at the west end of the stretch, when unaffected by picking up of the track relay 2TB, operates to supply an impulse of energy to the track rails once during every three cycles of operation of the code transmitter, but that if operation of the chain of transmitter relays is altered by picking up of the track relay 2TR, the impulse of energy may be supplied to the track rails after only two cycles of operation of the code transmitter, or the impulse of energy may not be supplied to the track rails until after four cycles of operation of the code transmitter.

The equipment is arranged so that the impulse of energy supplied to the track rails. will always be of the same length regardless of the effect of the track relay on the relay chain. As explained above, at times when the track relay is being operated by coded energy, the track battery is connected across the track rails during the first released period Of the code transmitter contacts following picking up of the relay ZCRA, while the relay ZCRA is picked up when the track relay is released and the contacts of the code transmitter are picked up. The relay ZCRA, therefore, positively checks that the track relay is released at the time the code transmitter contacts establish the circuit for the relay ZCRB. This arrangement insures that, if the relay ZCRB is picked up to supply energy from the track battery to the track rails, it will be picked up at the start of the released period of the code transmitter contacts and, therefore, will cause energy to be supplied to the track rails for the entire released period of the code transmitter contacts.

In addition, it will be seen that when the track relay 2TB. is picked up, its contact 28 interrupts the circuits of the relays ICRA, IC'RB and 2CRC so that they are certain to remain released and maintain the circuit for connecting the track relay 2IR. across the track rails. As a result there is no possibility that the track relay, when picked up, will be released because of interruption of its circuit by the relays 2CRA, ICRB and 2CRC. Accordingly, if foreign current is present in section 2-4T and picks up the track relay ITR, this relay will remain picked up and will not establish the circuit of relay 2TBP, which would occur if relay 2TB, released. As relay 2TB? remains released, the circuit of the winding of signal 28 is interrupted and this signal displays its stop indication.

Construction and operation. of code generating equipment at right-hand end of single track stretch The transmitter relays SCRA, 5CRB and SCRC and the code transmitter 561 associated with the track relay TR at the right-hand or east end of the track stretch (Fig. 1B), are arranged in substantially the same manner as the corresponding relays associated with track relay HR, and operate in substantially the same manner when the single track stretch is vacant so that track relay 5TB is operated by coded energy and contact 45 of relay BTFP is picked up. Under these conditions these transmitter relays operated to cause an impulse of energy to be supplied from the track battery 5TB to the track rails of sec tion l-ST in the first released period of the contacts of the code transmitter SCT following the period in which the code transmitter contacts are picked up and the contacts of the track relay 5TB are released.

When an impulse of energy is received over the rails of section 45T and picks up the contacts of the track relay STR, its contact 26a interrupts the circuits of the relays 5CRA, SCRB and SCRC so that any of these relays which are picked up release and so that all of these relays remain released as long as relay STR is picked up.

On release of relay 5TB energy is supplied over contact 230, which is governed in accordance with the position of switch 2W so as to be closed when and only when this switch occupies its normal position, front contact 25a of relay GTR and back contact 26a of track relay 5TH. to relay SCRA during the first picked-up period of the contacts of the code transmitter 501. The circuit for supplying energy to relay SCRA includes back contact 21a of relay SCRC and front contact Ha of code transmitter SCT, and when relay SCRA picks up, its contact 28a establishes a stick circuit to keep the relay picked up after release of contact ila of the code transmitter SCT. The equipment is now substantially in the condition designated step 2 in the chart above.

' On the first movement of the contacts of code transmitter SCI to their released position, energy is supplied to relay SCRB over the circuit which is traced from track relay contact 26a over front contact 29a of relay SCRA and back contact 39a of code transmitter SCI, and when relay SCRB picks up, its contact "a establishes a stick circuit for the relay. The equipment is now substantially in the condition designated step 3 in the chart above.

When relays SCRA and ICRB are picked up and relay BCRC is released, the track battery 5TB is connected across the track rails over the circuit which is traced from the positive terminal of the battery over back contacts Ila and 15a of relay SCRC in multiple. front contact lid of relay SCRB, front contacts Ila and 18a of relay SCRA in series, front contact [9a of relay CRB,

and back contact 20a of relay GDPR to one track rail, while the other terminal of the battery is connected over back contact 2la of relay GPDR to the other track rail.

During the second picked-up period of the contacts of code transmitter 5CT, energy is supplied to relay 5CRC over the circuit which is traced from contact 26a of track relay 5TB over front contacts 34a of relay 5CRB and front contact 35a of code transmitter 5CT. At this time, contact 210, of relay SCRC interrupts one stick circuit for relay SCRA, but relay SCRA is maintained energized by current supplied over front contact 29a of relay 5CRA and front contact 39a of code transmitter 5CT. In addition, at this time, relay 5CRB is energized by current supplied over its front contact 30a. The equipment is now substantially in the condition designated step 4 in the chart above.

When relay 5CRC picks up, its contacts Ma and l5a interrupt the previously traced circuit for connecting the battery 5TB across the track rails, and the track rails are now short-circuited over the circuit which is traced from one track rail over back contact Zia of relay BDPR, front contacts Ma and l5a of relay 5CRC in multiple, front contacts lie of relay 5CRB, front contacts Ila and l8a of relay 5CRA in series, front contact l9a of relay 5CRB, and back contact 20a of relay SDPR to the other track rail.

During the second released period of the contacts of the code transmitter, the supply of energy to relay SCRA is interrupted and it releases with the result that its contacts Ila and l8a interrupt the circuit for short-circuiting the track rails and connect the track relay 5TB. across the track rails. At this time energy is supplied to relay SCRB over the circuit which is traced from contact 26a of track relay 5TB over front contact 34a of relay 5CRB, back contact 35a of code transmitter SOT, and front contact 45 of relay 5TFP, so relay 5CRB remains energized. As relay 5CRB is picked up, energy is supplied over its front contact 34a and front contact 36a of relay 5CRC to relay 5CRC and it is maintained picked up, and the equipment is now in the condition designated step 5 in the chart above.

During the third picked-up period of the contacts of .the code transmitter 5CI, the supply of energy to relay 5CRB is interrupted and it releases, but at this time relay 5CRC is energized by current supplied over its front contact 21a and front contact 38a of code transmitter 5CT. The equipment is now in the condition designated step 8 in the chart above.

During the third released period of the contacts of the code transmitter, the circuit of the relay 5CRC is interrupted and it releases, while thereafter the cycle just described is repeated.

The description above assumes that the operation of relays 5CRA, 5CRB and 5CRC was not interrupted by picking up of relay 5TB, and that relay 5TFP remains picked up so that its contact 45 establishes the stick circuit by which relay 5CRB is maintained energized during the fifth step in the operating cycle. If the track relay 5TB picks up, its contact 26a is opened and the relays 5CRA, 5CRB and 5CRC release so that a new cycle of operation is started after release of relay 5TB.

The relay 5TFP is energized during the pickedup periods of track relay ITR and is snubbed by a condenser so as to be slow enough in releasing -to remain picked up longer than one cycle of operation of the transmitter relays 5CRA, SCRB and SCRC. Accordingly, if relay 5TR picks up once during each cycle of operation of the relay chain, the rela STFP remains picked up and its contact 45 is closed so that relay SCRB remains picked up during the fifth period in the operating cycle, and the relays 5CRA, SCRB and 5CRC operate on the threecode cycle basis described above, except as these relays are affected by picking up of the track relay. 7

When a train is in the single track stretch, the track relay 5TR remains released and after a short time interval the relay STFP releases and its contact 45 is open. Under these conditions the relay 5CRA picks up during the first picked-up period of the contacts of the code transmitter, that is, during the period forming the second step in a cycle, while relay SCRB is picked up during the first released period of the code transmitter, that is, during the period forming the third step in a cycle. At this time the track battery 5TB is connected across the track rails so energy is supplied to the track circuit. During the second picked-up period of the code transmitter, that is, during the period forming the fourth step in a cycle, the relays 5CRA and SCRB are maintained picked up and relay 5CRC is picked up, with the result that the supply of energy to the track rails is cut off and the track rails are short-circuited.

During the second released period of the code transmitter 501, which corresponds to the fifth step in the operating cycle outlined in the chart above, the. relay 5CRA is released, while the relay 5CRB is also released since the stick circuit for this relay is interrupted by contact 45 of relay 5'I'FP. As relay 5CRB releases, its contact 34a interrupts the stick circuit for relay 5CRC and it releases with the result that the equipment assumes the condition designated step I in the chart above.

Under these conditions, that is, when relay 5TFP is released, the relays SCRA, 5CRB and 5CRC complete one cycle of operation each two cycles of operation of the code transmitter contacts. The track battery is connected across the track rails during one of the four periods in these two cycles, and the track rails are shortcircuited during the succeeding one of the four periods. The track relay 5'I'R is connected across the track rails during the other two periods or steps in the cycle.

It will be seen that regardless of whether the equipment associated with track relay STR is operating on the two or the three cycle basis, the energy supplied to the track rails occurs during release of the code transmitter contacts following a picked-up period of its contacts in which the track relay is released. This insures that the impulses of energ supplied to the track rails will always be of the length determined by one-half a cycle of the code transmitter, and the impulses of energy supplied to the righthand end of the stretch are certain to be long enough to be transmitted through the inter mediate sections to the left-hand end of the stretch, but will not be so long as to interfere with transmission of impulses of coded energy over the single track stretch in the opposite direction.

As previously explained, when the single track stretch is occupied, the equipment at the lefthand or west end of the stretch (Fig. 1A) operates on a cycle which requires three cycles of the code transmitter 2CT, and the track battery 2TB is connected across the track rails during one of the six periods in the three code cycles, the track rails are short-circuited during the succeeding one of the six periods, and the track relay is connected across the track rails during the remaining four of the six periods.

Since during occupancy of the single track stretch the equipment at the two ends of the stretch operates at different rates, the impulses of energy supplied over the track rails from opposite ends of the stretch will not occur simultaneously for extended periods of time after the single track stretch is vacated. Instead, as soon as the single track stretch is vacated, there will promptly occur a time at which the track relay ITR is connected across the track rails and will respond to energy repeated from the west end of the stretch. Accordingly, the track relay STR will be picked up promptly when the single track stretch is vacated, and as soon as the track relay ITR picks up energy is supplied to relay BTFP and it picks up so that thereafter the equipment associated with track relay 5TB. operates to supply an impulse of energy to the section rails following release of the track relay, or, until the relay STFP releases, to supply an impulse of energy to the track rails once during each three cycles of operation of the code transmitter SCT.

Construction and operation of coded track circuit equipment for single track stretch The operation of the code detecting and impulse generating equipment at opposite ends of the single track stretch having been considered separately, the operation of the equipment for the single track stretch as a whole will now be considered.

When the equipment at the left-hand end of the stretch, Fig. 1A, operates to supply an impulse of energy to the rails of section 2--3T, one or the other of the track relays BHTR or 3DTR picks up, the one depending on the polarity of the impulse of energy. The polarity of the energy supplied to the west end of section 23T is governed by relay IDPR so that energy of reverse or normal polarity is supplied to the rails of section 2-3T according as relay IDPR is released or is picked up. The relay I DPR is normally released, and is picked up when and only when the signal IS displays its green-or clear indication. The signal iS is normally dark and its winding is normally deenergized so that the signal, if lighted, would display its red or stop indication.

As relay IDPR is normally released, energy of reverse polarity is normally supplied to the rails of section 2-31 from battery 2TB. At these times the positive terminal of the battery is connected to the upper track rail I. At the east or right-hand end of section 2-3T, the track relays 1 SHTR and 3DTR are normally connected in series across the section rails over the back contact of track relay 3-4ETR. The track relays lHTR and 3DTR are of the polar biased neutral type having normally released contacts which are picked up when and only when energy flows through the relay winding in a. selected direction as indicated by the arrows on the relay windings.

'The relays JHTR and 3DTR are connected with the track rails so that relay IHTR picks up when positive energy flows from rail l to rail 2, and

16 relay IDTR. picks up when positive energy flow! fromrailitoraili.

When relay SHTR picks up, energy is supplied over one of its front contacts from battery 3-4WTB to the rails of section 3-4T. At this time the negative terminal of the battery 34W'I'B is connected to track rail 2, while the positive terminal of the battery is connected through the winding of relay 34ETR to track rail i. As explained in Letters Patent of the United States No. 2,286,002, issued June 9, 1942, to Frank H. Nicholson for Railway signaling system, the energy supplied from the battery 3-4WI'B flows through the winding of track relay 3-4ETR in the wrong direction to pick up the relay contacts and they remain released at this time.

If relay IDPR is picked up and the code generating means operates to connect the track battery 2TB across the track rails, the negative terminal of the battery will be connected over front contact 2! of relay IDPR to the upper track rail I, and the energy supplied to the track rails will be of normal polarity. This energy will pick up the contacts of relay SDTR, but will not pick up the contacts of relay SHTR. When relay SDTR picks up, one of its contacts establishes a circuit for supplying energy from battery l-lWTB through the winding of relay l-lETR to the rails of section 3-4T.

The'relays SHTR and JDTR control code detecting means for selectively controlling a distant signal, not shown, for governing movement of westbound traflic approaching the passing siding I. This signal control means is not a part of this invention, and has been omitted in order to simplify this disclosure.

The energy supplied from battery 3-4WTB to the rails of section 3-4T feeds over back contacts of track relays tDTR and lHTR. to relay I-JWTR and picks up its contact to supply energy from battery 45WTB to the rails of section l-ST.

The energy supplied from battery 4-5WTB to the rails of section l-ST feeds to relay BTR over the circuit which is traced from track rail I through the winding of relay STR, and over back contacts lid and 18a of relay SCRA in series to track rail 2. This energy picks up the contacts of track relay 5TH. so that contact 26a interrupts the circuits of relays SCRA, BCRB and SCRC, while contact of relay 5TB establishes the circuit of relay BTFP.

It will be seen, therefore, that when the single track stretch is vacant and energy is supplied to the west end of the stretch, it is repeated through the successive track sections to the right-hand or east end of the stretch to pick up the track relay 5TB at that point.

After a short interval the supply of energy to the west end of the stretch is cut off and the rails of section 23T are short-circuited. This results in release of relay SHTR, or relay SDTR, if it had been picked up, so that the supply of energy from battery 3-4WTB to the rails of section HT is cut on. When the supply of energy to the rails of section I-4T is cut cit, relay HWTR releases and cuts oil the supply of energy to section l-IT and relay STR releases so that its back contact 26a is closed with the result that energy is supplied to relay SCRA when the contacts of the code transmitter ICT tact 28a of relay I'I'R. and by front contact ll of relay ISR. so that energy is supplied over this circuit only if section IT is vacant or is occupied by an eastbound train.

If .traflic conditions are such that energy is supplied to the circuit governed by back contact Ila of relay TB; the relays ICRA, ICRB and CBC will operate as previously explained to cause an impulse of coordinated return code energy to be supplied from battery ITB to the rails of section 4-5T. This energy impulse is of reverse or normal polarity according as the relay lDPR is released or is picked up. The relay ODPR is controlled by entering signal S and is picked up when and only when the signal is conditioned to display its'green or clear indication. The signal BS, like the signal IS, is normally dark and its winding is normally deenergized so that the signal, if lighted, would display its red or stop indication.

The winding of signal 88 is assumed to be deenergized so the relay ODPR is released, as

shown, and the energy impulses supplied from battery 5TB to the rails of section 4-iT are of reverse polarity and operate the track relay HTR. but will not operate the track relay lDTR. The relays lI-ITR and lDTR are of the polar biased type and each will respond to energy of one polarity only and the two relays are connected to the rails in such manner that they respond to energy of opposite polarity.

when relay IHTR picks up, energy is supplied over one of its front contacts from battery l-lETB to the rails of section l4T. The battery s-m'rn is connected through the winding of relay l-JWTR in the wrong direction to pick up the relay contacts.

If relay BDPR is picked up, the energy impulses supplied from battery ITB to the rails of section 4 5T will be of normal polarity and will pick up the contacts of relay lDTl-t so that one of its contacts establishes a circuit for supplying energy from battery HETB through the grinding of relay 34WTR to the rails of section The relays lDTR and lHTR control code detecting means for selectively controlling a distant signal, not shown, for governing eastbound traflic approaching the passing siding II, but this means is not a part of this invention and has been omitted in order to simplify this disclosure.

The energy supplied to the rails of section 3-4T feeds to relay 3'4ETR. over back contacts of relays 3HTR and 3DTR. and relay 3-4ETR picks up to cause energy to be supplied from battery 2--3ETB to the rails of section 2-3T. The energy supplied from battery 2-3ETB to the rails of section 2-3T feeds to track relay 2TB and picks up its contacts to energize relay ZTF'P, while contact 26 interrupts the circuits of relays ZCRA, 2CRB and 2CRC to release any of these relays which are picked up.

After a short time interval the equipment at the right-hand or east end of the single track stretch cuts off the supply of energy from battery 5TB to the rails of section l-5 T, which results in the release of relay lHTR, or of relay lDTR, if it had been picked up, and cuts off the supply of energy from battery 3-4ETB, and relay'S-JETR releases to cut off the supply of energy from battery 2--3ETB to the rails of section 2-3T.

When the supply of energy from battery 2-3ETB is cut off, the track relay 2TB releases so that its back contact 28 is closed, while its contact ll interrupts the supply 0! energy to relay 2TB? and establishes the circuit including front contact I of relay ITFP for energizing relay 2TBP. The relay ZTFP has a condenser connected across its terminals to make the relay slow enough in releasing to remain picked up in the intervals between picked-up periods of the relay 2TB. A condenser is connected across the terminals of relay 2TB? over a circuit including front contact OI of relay ITFP so the relay 2TB! remains picked up during the pickedup periods of relay 2TB, but releases promptly on release of relay ITFP.

As previously explained, during the pickedup period of the track relay 2TB its contact 2| interrupts the circuits of the transmitter relays 2CRA, ZCRB and 2CRC, and all of these relays are released, while on release of relay 2TB. and consequent closing of its back contact ll, energy may again be supplied to the relays ICRA, 2033 and ICRC over the circuits governed by the contacts of the code transmitter ICT so that an impulse of energy is supplied from the track battery 2TB and is repeated throughout the single track stretch.

As longas the single track stretch is vacant.

the operation just described is repeated, that is.

an impulse of energy is supplied to the left-hand or west end of the stretch and is repeated throughout the stretch to the right-hand or east end where it picks up the track relay TR to energize the code detecting relays STFP and STBP, and to release the transmitter relays and thus cause an impulse oi. coordinated return code energy to be supplied to the east end of the stretch promptly upon release of the track relay. The impulse of energy supplied to the east end of the stretch is repeated throughout the stretch to the west end where it picks up the track relay 2TB. to energize the code detectingrelays ITFP and ZTBP, and to release the transmitter relays and thus cause an impulse of coordinated return code energy to be supplied to the west end oi! the stretch promptly upon release of the track relay.

Accordingly, as longas the stretch is vacant, the code generating means at both ends of the stretch operates on a coordinated return code basis and impulses or energy are transmitted over the single track stretch alternately in opposite directions.

' As a result of operation of the track relays 2TH. and 5TB, the relays ITBP and STBP at the ends of the single track stretch are maintained picked up. Accordingly, contacts I50 and i5! of relay 2TB? establish the circuit of the winding of signal 23 so this signal will display its green or clear indication. Similarly, contacts H5 and H8 of the relay STBP establish the circuit of the winding of signal is so that this signal will display its green or clear indication.

As explained in the above-identified application of Henry S. Young, the circuits of the windings of the signals 25 and is may be approach controlled so as to be complete only on the approach 01' a train. However, this control of the circuits of these signals is not essential to an understanding of this invention and has been omitted in order to simplify this disclosure.

From the foregoing it will be seen that when the single track stretch is not occupied the equipment at an end of the stretch operates at intervals to supply an impulse of energy of accurately measured length to the track rails.

76 This energy picks up the track relay at the opposite end of the section at that end of the single track stretch so that it connects the track battery across the rails of the adjoining section, with the result that this operation is repeated throughout the stretch. At the'termination of the impulse supplied to the end of the stretch,

the track relay for the section at this end of the stretch releases and interrupts the supply of energy to the adjoining section, and this operation is repeated throughout the stretch. The code generating equipment at an end of the stretch operates to shunt the rails of the end track section for a short time immediately after the supply of energy to this section. This dissi pates energy stored in the track circuit for this track section but has no effect on the energy stored in the track circuits of the other track sections in the stretch.

When the supply of energy to an end of the stretch is cut off, the track relays throughout the stretch release successively, and although these relays are of a type which respond promptly they do not respond instantaneously, so there is a short time interval from the instant at which the supply f energy to one end of the stretch is out d and the instant at which the back contact of the track relay at the opposite end of the stretch is closed. During at least a portion of this time interval the supply of energy from the track batteries to the rails of the various sections continues.

When the track relay at an end of the stretch is picked up, the transmitter relays CRA, CRB and CBC associated with this track relay are all released. When the track relay at an end of the stretch releases, its back contact in the circuit of the transmitter relays is closed.

If at the time the track relay releases the code transmitter contacts are picked up, the

relay ERA will pick up at once and at the end contacts of the code transmitter are released,-

the relay C'RA will not be picked up until the code transmitter contacts move to their pickedup position, while the relay CRB will not be picked up to cause energy to be supplied to the rails of the single track stretch until the code transmitter contacts subsequently move to their released positions.

If the track relay releases at a time when the code transmitter is near the end of a picked-up period, energy will be supplied to the track rails very soon after release of the track relay. On the other hand, if the track relay releases when the code transmitter is near the beginning of a released period, energy will not be supplied to the track rails for almost a complete cycle of operation of the code transmitter after the release of the track relay.

The code transmitters at the opposite ends of a track stretch operate continuously and are entirely independent of each other and of the track circuit apparatus. The code transmitters at the opposite ends of a stretch are, of the same nominal code speed, but because of manufacturing variations in them, they will not operate at exactly the same code speed. As a result the relationship of the contacts of the two code transmitters to each other will be constantly changing, and the position of the code transmitter contacts on release of the associated track relay will be constantly changing.

Furthermore, the length 0! time which must elapse from the instant at which the supply of energy to one end of the stretch is cut oil until the track relay at the other end of the stretch releases will vary with the number and the length of the sections in the stretch, and will also vary with changes in operating conditions, such as changes in track ballast resistance and battery voltage.

Because of the variation. in the factors affecting the frequency of the supply of energy impulses to the ends of the stretch, the supply of these impulses will fluctuate and will be somewhat irregular, but impulses of energy will be transmitted over the rails of the stretch in each direction frequently enough to maintain the code detecting relays at both ends of the stretch picked up.

Furthermore, the operation of the equipment is such that the time during which energy is supplied to a section at both ends is less than onehalf of the total time. During th supply of energy to the rails of a section a charge is built up in the track ballast of the track section, while the energy thus stored in the ballast discharges during the intervals between energy impulses. The longer the energy impulses the higher the value of the charge built up in the track ballast, while the longer the intervals between energy impulses the greater the discharge of energy stored in the track ballast. Accordingly, the average value of the charge in the track ballast is governed by the proportion of the time during which energy is supplied to the track rails.

If too high a charge is developed in the track ballast of a track section, it will delay the release of the track relay for the track section. Where an impulse of track circuit energy is repeated or relayed from one section to an adjoining section by the front contact of a track relay, any delay in the release 01' the track relay results in prolongation of the impulse supplied to the adjoining section. Where the impulses must be repeatedthrough several track sections by front contact coding, any distortion of the code impulses resulting from delay in the release of the track relays is cumulative, and, if release of the track relays is delayed for an appreciabl time interval, the code impulses may be distorted to an objectionable degree.

Since this system is arranged so that energy is supplied to the rails of a track section for less than one-half of the total time, the charge built up in the ballast of the track sections will not be high enough to materially delay release of the track relays, and the impulses of track circuit energy will not be obiectionably distorted.

Operation of equipment on movement of an eastbound train through the stretch When an eastbound train occupies section II in the main track portion beside the passing siding I, the track relay ITR is released and its contact 25 interrupts the circuit including back contact 26 of track relay HR for supplying energy to the transmitter relays ZCRA, ZCRB and 2CRC. Accordingly, these relays release and thereafter remain released so that the track relay 2'I'R is connected across the track rails while energy is no longer supplied from battery 2TB to the rails of the stretch. As impulses of coded energy are not supplied to the west end of section 2-3T, energy is no longer supplied to the west end of the other sections in the stretch and relay 5TB remains released and does not establish the circuit 2* of relay i'I'FP. After a short time interval the relay rm releases and interrupts th circuit for supplying energy torelay BTBP and also interrupts the circuit by which the condenser is connected across the terminals of the winding i of relay I'IBP so the relay lTBP releases promptly on release'of relay UTFP. When relay S'I'BP releases, its contacts III and Ill interrupt the circuit of the winding of signal 53 to insurethat it displays its red or stop indication and thus prevents entrance of a westboundtrain into the single track stretch.

a are repeated throughout the various sections in the stretch so the relay ITR continues to operate and relays I'IFP and 2TB? are maintained picked up. As relay 2TB? is picked up its contacts I50 and lil maintain the circuit of the winding of signal 28 and this signal continues to display its green or clear indication and authorizes the eastbound train to advance into the single track stretch.

When the eastbound train advances into section 2-3T, the track relay ZTR. ceases to operate and relays 2TF'P and ITBP release so that contacts I" and lil of relay ZTBP interrupt the circuit of the winding of signal 25 and this signal now displays its red or stop indication.

When the eastbound train vacates section IT, the track relay ITR picks up so that its contact 25 establishes the circuit including back contact 26 of track relay 2TH for supplying energy to the transmitter relays ICRA, 2CRB and ZCRC and these relays again operate to supply energy from battery 2TB to the rails of section 2-3T..

However, because of the presence of the train in the single track stretch, the energy impulses supplied to the left-hand or west end of the stretch do not reach the east end of the stretch and the relay TB remains released.

As long as the single track stretch is occupied, therefore, the track relays 2TB and 5TB at the opposite ends of the single track'stretch both remain released and the associated code detecting' relays are deener'gized so the head block signals 28 and is both display their red or stop indications. 1 r

As the train advances through the single track stretch it progressively cuts off the supply of energy from right to left over the rails of the various sections, while coded energy supplied to the left-hand or west end of the single trackstretch is repeated in each of the sections behind the train.

For purposes of illustration it will be assumed that as the train approaches the passing siding II the entering signal 68 is displaying a permissive indication so that a contact of the signal mechanismpestablishes the circuit for one of the relays GDPR or SHPR.

When the eastbound train passes signal 6S and enters section ET, the track relay G'IR. releases and its front contact a in the circuit of the transmitter relays SCRA, SCRB and 5012.0 is opened, while energy is supplied over back contact 25a and a front contact of one of the relays BDPR or OHPR to relay 65R and'it picks up to establish its stick circuit to keep its contacts picked up as long as relay lTR-is released. On;

releaseof relay ITR, the signal '68 is put to] stop by means not shown. and the relay ODPR' or BHPR, which was picked up, releases and in-[ terrupts the pick-up circuit for relay ISR. However, relay 68R picks up before its pick-up circult'is interrupted, and is maintained energized by current suppliedover its stick circuit after its pick-up circuit is interrupted.

when relay BSR picks up, its contact 8! establishes a circuit for supplying energy to the transmitter relays BCRA, CR3 and SCRC, and they continue to operate to supply impulses of energy to the track stgetch. and to connect the track relay TR. across the track rails.

When the train vacates section 4-5T the coded energy supplied to the left-hand or west end of the section rails as a result of the supply of energy to the left-hand or west end of the single track stretch feeds to track relay BTR and picks up its contacts so that its contact 80 establishes the circuit of relay STFP and it picks up to close its front contact in the stick circuit for'relay SCRB, and the transmitter relays SCRA,

BCRB and SCRC now operate on the coordinated return code basis instead of on the two code cycle basis.

As previously explained, when the stretch is occupied, the transmitter relays at the righthand end of the stretch operate to supply an impulse of energy to the track rails once during everytwo cycles of operation of the code transmitter SC'I', while the transmitter relays at the left-hand end of the stretch operate to supply a an impulse of energy to the track rails once during every three cycles of operation of the code transmitter ZCT. Because of this difierence in the rate of operation of the apparatus at opposite ends of the single track'stretch, when the single track, stretch is vacated, there will promptly occur a time at which an impulse of energy supplied to one end of the stretch will feed to the track relay at the other end. The equipment at each end of the stretch operates to supply an impulse of energy to the rails of the stretch promptly after release of the associated track relay, and this impulse will be transmitted over the rails of the stretch. to the opposite end to pick up the track relay at that location.

' Accordingly, when the single track stretch is vacated, an impulse of energy will be quickly supplied to relay 5TB and it will operate to energize; relays 5'I'FP and STBP. When relay STEP picks up, its contact, 45 in the stick circuit for relay SCRB is closed, and the transmitter relays SCRA, SCRB and SCRC now-operate on the coordinated return code basis instead of on thebasis of two cycles of the code transmitter 501. When the single track stretch is vacated and Q the track relays 2'I'R. and HR are operated by energy supplied over the track rails, the relays 2TB? and STBP are picked up and establish the circuits of the windings of the signals 23 and 55 so that these signals both display their green or clear indications.

When the train advances contact 25a interrupts-the circuit of relay SR and establishes a circuit for supplying energy to the transmitter relays SCRA, SCRB and 'SCRC after release of relay GSR and opening of its contact 8i. The equipment is-now substantially in the condition in which it is shown in the drawings.

far enough to. vacate section 6T, the track relay GTR picks up and its a Operation of eguipment on movement of a westbound train through the stretch During movement of a westbound train through the stretch the equipment operates in substantially the same manner as during movement of an eastbound train through the stretch.

For purposes of illustration it will be assumed that the track stretch is vacant so that the code generating means at both ends of the single track stretch operates to supply coded energy to the track rails with the result that relays 2TB! and STBP are picked up and cause the head block signals 28 and ES to display clear indications.

If a westbound train now enters section 5T, the track relay STR will release and its contact 25a will interrupt the circuit for supplying energy to the transmitted relays SCRA, SCRB and SCRC and they cease to operate to supply impulses of energy to the track rails. At this time the signal SS is at stop so the relays GDPR and SHPR' are both released and on release of relay 8TB the relay ESE remains released and does not establish a circuit for supplying energy to the transmitter relays.

When the supply of coded energy to the east or right-hand end of the singletrack stretch is cut ofl, the supply of energy to the right-hand end of the various sections in the stretch ceases, and relay 2TB remains released. After a short time interval relay QTFP releases and its contact 90 interrupts the circuit of relay ZTBP so that it releases and interrupts the circuit of the winding of signal 28 and thus insures that this signal will display its red or stop indication.

At this time the transmitter relays ICRA, 2CRB and ZCRC continue to operate to supply impulses of energy to the left-hand 'end of the stretch and these impulses are repeated through the various sections to the right-hand end of the stretch and operate track relay BTR to keep relay 5TB energized and thus maintain the display of the clear indication by signal is.

when the train passes signal is and enters the single track stretch, relay STR remains released and after a short time interval relays 5TFP and STBP release with the result that the supply of energy to the winding of signal 55 is cut off and this signal displays its red or stop indication.

When the train vacates section ET, the track relay 6TB picks up and its contact 25a establishes the circuit. for supplying energy to the transmitter relays SCRA, SCRB and SCRC and these relays now operate to cause impulses of energy to be supplied to the track stretch. As the relay STFP is released its contact 45 interrupts the stick circuit for the relay SCRB so the transmltter relays operate to supply an impulse of energy to the track rails once during every two cycles of operation of the code transmitter SCT. As the single track stretch is occupied the impulses of energy supplied to the right-hand end of the stretch do not reach the left-hand end of the stretch so the relay 2TH,- remains released and causes signal 25 to display its stop indication.

As the train proceeds through the track stretch the supply of coded energy from left to'right over the rails of various sections is progressively cut off, while coded energy is supplied from right to left over the sections behind the train.

For purposes of illustration it will be assumed that the westbound train is to enter the passing siding I. The train is stopped short of the siding, and one of the train crew reverses the switch IW, and as a result contact 23 interrupts negative terminal of the battery, and from the 2 the circuit for supplying energy to the transmitter relays 2CRA, ICRB and ICRC and they cease to operate. In addition, contact 23 interrupts the circuit of relay ISR so that it remains released when the train passes through the siding section and relay ITR is released.

When the train completes its movement into the siding and the switch [W is restored to its normal position, energy is again supplied to the transmitter relays ZCRA, ICRZB and ICRC over the circuit governed by the switch controlled contact 23 and front contact 25 of relay ITR. Accordingly, these transmitter relays again operate to supply impulses of coded energy to the track rails, while the track relay I'I'R will respond to impulses oi. energy supplied over the track rails.

As explained above, the code generating equipment at the two ends of the stretch, when unailected by receipt of energy impulses over the stretch, operates at different rates so that when the stretch is vacated and coded energy is again supplied in both directions over the rails of the stretch, the coordinated operation of the two sets of code generating equipment is promptly resumed. In addition, the track relays ZTR and 5TH, operate and energize the associated code detecting relays so that they cause the signals 28 and 58 to display their green or clear indications.

Modification shown in Fig. 20f the drawings In Fig. 2 of the drawings there is shown a modilied form of code generating means which may be employed when only one polarity of energy is supplied to the track rails, as is the case if line wires, instead of polarized track circuit energy are employed for controlling the distant signal When the energy supplied from the track bat tery is always of the same polarity, the circuits of the track relay and track battery may be arranged as shown in Letters Patent 01 the United States No. 2,286,002 to Frank H. Nicholson to prevent improper operation of thetrack relay 2TR- by energy from the track battery ITBin the event the front and back contacts of one of the transmitter relay contacts should overlap orbe 'closed concurrently.

The modification shown in Fig. 2 diilers from that shown in Fig. 1 only in the arrangement of the circuits oi the track relay 2TB and of the track battery 2TB. In the species shown in Fig. 2 the circuits for operating the transmitter relays 2CRA, 2CRB and ICRC by the code transmitter 2CT are exactly the same as in Fig. 1, and these relays pick up and release cyclically in the manner explained in detail in connection with Fig. 1.

The equipment is shown in Fig. 2 in the condition which it assumes when the track battery 2TB is connected across the track rails, that is, when the transmitter relays are in the condition designated step 3 in the chart above. At this time the contacts of relays ICRA and ICRB are picked up and the contacts oi relay ICRC are released with the result that the track battery 2TB is connected across the track rails over the circuit which is traced from track rail 2 to the positive terminal of the battery over front contacts Ill: and 18b of relay ICRA in parallel, front contacts lib and lib oi relay'lCRB in parallel, back contacts llb and Nib of relay ICRC in parallel, and thence to track rail I through the winding of track relay 2TB in the wrong direction to pick up the relay contacts.

when the contacts oi the code transmitter 26'! pick up, a circuit is established to pick up the contacts of relay 2CRC with the result that its contacts I lb and lib interrupt the circuit traced above for connecting the track battery 2TB across the tracfi'iilsand connect the track relay 2TH. across the track rails over an obvious circuit. On interruption of the supply of energy from the battery. IT]; to the track rails an impulse of energy may be inductively discharged from the track circuit. This energy will flow in the same direction as the energy previously supplied from the track battery and flows through the winding of the track relay in the wrong direction to pick up the track relay contacts and therefore cannot produce objectionable operation of the relay.

As will be apparent from the chart given above relays 2CRA and 2CRB release, the track relay.

2TB. is unailected since it is connected across the track rails over front contacts of relay ICRC, and the circuit of the track relay is independent or relays 2CRA and ICRB.

During the flrst step in a new cycle of operation of the transmitter relays,they are all released and the track relay ITR. is connected,

across the track rails over the circuit which includes back contacts lib and llb of relay ICRB in parallel, and back contacts Nb and lib of relay ICRC'in parallel.

During the second step in the new code cycle the relay 2CRA picks up, but this does not aflect the track relay since the contacts of relay ICRA are not included in the circuit of the track relay.

During the third step in the new cycle the relay ICRB picks up and interrupts the circuit for connecting the track relay across the track rails and establishes the circuit for connecting the track battery across the track rails in series with the winding of the track relay.

From the foregoing it will be seen that this modification, like that shown in Fig. l,'is arranged so that energy is supplied-from the track battery to the track rails during the third step in the cycle of operation of the transmitter re- .across the track rails instead of the track rails being short-circuited. Accordingly, in the modification shown in Fig. 2, the track relay is connected across the track rails so as to be able. to respond to energy supplied over the track rails during five out of the six steps in the cycle of operation of the transmitter relays.

As the energy for operating the transmitter relays is supplied over a circuit which includes a back contact of the track relay 2TB, picking up of the track relay 2TB results in release of any ofthe transmitter relays which are picked If the track relay 2TB picks up at a time during which it is connected across the track rails over front contacts of relay ICRC, the relay ICRC will release because its circuit is opened at contact 26 of the track relay ITR, and during move- 26 ment of the contacts of relay 2CRC between their picked-up and released positions the circuit of the track relay will be interrupted but this interruption is so short that the track relay remains picked up.

Although only the code generatingequipment for only the left-hand end of the single track stretch has been shown in Fig. 2, it is obvious that the circuits of the track relay and track battery at the right-hand end of the stretch can be arranged in the same manner where the energy supplied from the track battery to the track rails is of only one polarity.

Operating characteristics of code generating means This code generating means is arranged so that no failure of the equipment to operate as intended can create a hazardous condition.

Referring to Fig. 1A it will be seen that, if for any reason the relay 2CRA will not pick up, its

, the track rails and energy will not be contact 28 will not establish the pick-up circuit for relay ZCRB and it will remain released and will prevent relay 2CRC from picking up. Under these conditions, all of the transmitter relays remain released and the track relay ZTR will be continuously connected across the track rails, but energy will not be supplied from track battery 2TB to the track rails. The absence of the supply of energy from battery 2TB to the track rails holds the westbound signals at stop, but cannot create a dangerous condition.

If relay ICRA should remain picked up and fail to release, its contact i1 and It may interrupt the circuit of the track relay ITR and thus prevent its response to energy supplied over the track rails. This will prevent clearing of signal 28, but will not create a. dangerous condition. When relay ZCR'A is continuously picked up, the relays ICRB and 2CRC may pick up and remain picked up continuously, thus not only interrupting the circuit of the track relay 2TB but also preventing the supply of energy from the battery 2TB to the track rails.

If the pick-up circuit for relay ZCRB is defec tive so that the relay will not pick up, the trackv relay 2TR will be continuously connected across supplied to the track rails from battery 2TB.

If for any reason the relay ZCRB remains picked up continuously, the relay 2CRC will also be picked up continuously to prevent the supply of energy'from battery 2TB and to short-circuitthe track rails if relay 2CRA should pick up. When relay ZCRC is picked up, the pick-up circuit for relay 2CRA is interrupted at back contact 21 of relay 2CRC, so the relay ZCRA remains released and connects track relay 2TB across the track rails.

If the stick circuitfor relay ZCRB is defective, the relay may release during the fourth step in the cycle of operation of the transmitter relays. that is, during the step immediately following the suppl of energy from the track battery to the track rails. However, the relay ZCRB is snubbed by a rectifier and will not release instantaneously, and prior to release of relay ICRB the relay ICRC will pick up to interrupt the circuit of the track battery and to short-circuit the track rails. When the supply of energy from the track battery is cut 01!, the energy inductively discharged from the track circuit is discharged at once and will be dissipated through the short-circuit connection established when relay 2CRC is picked up. This impulse of energy inductively discharged from the I 27 track circuit is of very brief duration and will be completed before the relay ICRB releases to connect the track relay across the track rails, and therefore cannot cause improper operation of the track relay even under the abnormal condition under consideration, that is, when the stick circuit for relay 2CRB is defective.

If the pick-up circuit for relay 2CRC is defective so that this relay will not pick up, the relays 2CRA and 2CRB will pick up and remain picked up continuously. This will cause the track battery to be continuously connected across the track rails and the circuit of the relay 2TB to be continuously interrupted. Under these conditions the signals for both directions of trafiic are held at sto If the stick circuit for relay 2CRC is defective so that this relay releases prematurely, its back contact 2'? in the pick-up circuit for relay ZCR-A will be closed and a new cycle of operation of the relays ZCRA, ZCRB and ZCRC will be started sooner than it should be. This may result in too frequent supply of energy from the battery 2TB to the track rails but this cannot create a hazardout condition since the signal indications are in no way affected by changes in the frequency of the impulses of track circuit energy. Under these conditions the track relay 2TH may be connected across the track rails for such short periods that it will not be operated by energy supplied over the track rails. This will prevent clearing of signal 25 but does not create a hazardous situation.

From the foregoing it is clear that if for any reason the transmitted relays at the left-hand end of the single track stretch and shown in Fig. 1A of the drawings fail to operate as intended, the signals for one or both directions of traihc in the single track stretch may be held at stop, but that this failure of the transmitter relays cannot result in the improper clearing of a signal.

Although the foregoing analysis is directed specifically to the transmitter relays shown in Fig. 1A, it applies equally well to the transmitter relays shown in Figs. 13 and 2 as they are also arranged so that any failure to operate as intended may prevent clearing of the signals for one or both di rections of trafiic in the single track stretch but cannot result in improper clearing of a signal.

Although I have herein shown and described only one form of code generating means embodying my invention together with one modification thereof, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a coded railway signaling system for a section of railway track having a code following track relay responsive to impulses of energy supplied over the rails of said section, code generating means for supplying said impulses of energy to the rails of said section, said code generating means comprising a code transmitter having contacts which are continuously operated between a first and a second position at a selected rate, a plurality of transmitter relays, circuit means governed by contacts of said code transmitter and of said transmitter relays for cyclically governing said transmitter relays so that on each movement of the contacts of the code transmitter the contacts of a different one of said transmitter relays are moved from their first to their second position until the contacts of all of the transmitter relays occupy their second position and so that thereafter on each movement of the contacts of the code transmitter the contacts of a different one of said transmitter relays are moved from their second to their first position until the contacts of all of the transmitter relays occupy their first position, and a circuit governed by said transmitter relays for connecting a source of energy across the rails of said section during one and only one step in the cycle of operation of said transmitter relays.

2. In a coded railway signaling system for a section of railway track having a code following track relay responsive to impulses of energy supplied over the rails of said section, code generating means for supplying said impulses of energy to the rails of said section, said code generating means comprising a code transmitted having contacts which are continuously operated between a first and a second position at a selected rate, a plurality of transmitter relays each having contacts movable between a picked-up position, pick-up and stick circuits for each of said transmitter relays governed by contacts of said code transmitter and of said transmitter relays for cyclically governing said transmitter relays so that on each movement of the contacts of the code transmitter the contacts of a different one of said transmitter relays are picked up until the contacts of all of said transmitter relays are picked up and so that thereafter on each movement of the contacts of the code transmitter the contacts of a different one of said transmitter relays are released until the contacts of all of said transmitter relays are released, and a circuit governed by sadi transmitter relays for connecting a source of energy across the rails of said section during one and only one step in the cycle of operation of said transmitter relays.

3. In a coded railway signaling system for a section of railway track having a code following track relay responsive to impulses of energy supplied over the rails of said section, code generating means for supplying said impulses of energy to the rails of said section, said code generating means comprising a code transmitter having contacts which are continuously operated between a first and a second position at a selected rate, three transmitter relays each having contacts movable between a released and a picked-up position, pick-up and stick circuits for each of said transmitter relays governed by contacts of said code transmitter and of said transmitter relays for cyclically governing said transmitter relays so that on each movement of the contacts of said code transmitter a different one of said transmitter relays is picked up until all three of said relays are picked up and so that thereafter on each movement of the contacts of said code transmitter the contacts of a difierent one of said transmitter relays are released until the contacts of all three of said transmitter relays are released, and a circuit governed by said transmitter relays for connecting a source of energy across the rails 01 said section during one and only one step in the cycle of operation of said transmitter relays.

4. In a coded railway signaling system for a section of railway track having a code following track relay responsive to impulses of energy supplied over the rails of said section, code generating means for supplying said impulses of energy to the rails of said section, said code generating means comprising a code transmitter having contacts which are continuously operated between a first and a second position at a selected rate,

a first, a second and athird transmitter relay each having contacts movable between a released and a picked-up position. a pick-up circuit for said first transmitter relay including a back contact of said third transmitter relay and a first position contact of said code transmitter, a pick-up circuit for said second transmitter relay including a back contact of said third transmitter relay and a front contact of said first transmitter relay and a second position contact of said code transmitter, a pick-up circuit for said third transmitter relay including a front contact of said second transmitter relay and a first position contact of said code transmitter, said first' transmitter relay when picked up establishing stick circuits to maintain itself picked up until the contacts of said third transmitter relay are picked up and the code transmitter contacts are in their second position, said second, transmitter relay when picked up establishing stick circuits to maintain itself picked up until the contacts of the first transmitter relay are released and the code transmitter contacts are in their first position, said third transmitter relay when picked up establishing stick circuits to maintain itself picked up until the contacts of said first and second transmitter relays are released and the code transmitterccontacts are in their second position, and a circuit governed by said transmitter relays for connecting a source of energy across the rails of said section during one and only one step in the cycle of operation of said transmitter relays.

5. In a coded railway signaling system for a section of railway track havingv a code following track relay responsive to impulses of energy supplied over the rails of said section, code generating means for supplying said impulses of energy to the rails of said section, said code generating means comprising a code transmitter having contacts which are continuously operated between a first and a second position at a selected rate, a first, a second and a third transmitter relay each having contacts movable between a released and a picked-up position, a pick-up circuit for said first transmitter relay including a back contact or said third transmitter relay and a first position contact of said code transmitter, a'

pick-up circuit for said second transmitter relay including a back contact of said third transmitter relay and a front contact of said first transmitter relay and a second position contact of said code transmitter, a pick-up circuit for said third transmitter relay including afront contact of said second transmitter relay and a first position contact of said code transmitter, said first transmitter relay when picked up establishing stick circuits to maintain itself picked up until the contacts of said third transmitter relay are picked up and the code transmitter contacts are in their second position, said second transmitter relay when picked up establishing stick circuits to maintain itself picked up until the contacts of the first transmitter relay are released and the code transmitter contacts are in their first position, said third transmitter relay when picked up establishing stick circuits to maintain itself picked up until the contacts of said first and second transmitter relays are released and the code transmitter contacts are in their second position, and a circuit including a front contact of said second transmitter relay and a back contact of said third transmitter relay for connecting a source of energy across the rails of said section.

- 8. In a coded railway signaling system, in combination, a stretch of railway track through which trafilc may move in either direction, a code following track relay at each end of the stretch governed by coded energy supplied over the rails of the stretch, codedetecting means associated with each track relay and responsive to operation theregf, a signal at each end of the track stretch governed by the associated code detecting means, and code generating means at each end of the stretch for supplying impulses of energy to the rails of the stretch, each of said code generating means comprising a code transmitter having contacts which are continuously operated between a first and a second position at a selected rate, three transmitter relays each having contacts movable between a released and a picked-up position, pick-up and stick circuits for each of said transmitter relays including a back contact of the associated track relay, the pick-up and stick circuits for the transmitter relays at each end of the stretch being governed by contacts of the associated code transmitter and of the transmitter relays at that end of the stretch so that on each movement of the contacts of said code transmitter a difierent one of said transmitter relays is picked up until all three of said relays are picked up and so that thereafter on each movement of the contacts of said code transmitter the contacts of a diil'erent one of said transmitter relays are released until the contacts of all three of said transmitter relays are released, and a circuit governed by said transmitter relays for connecting a source of energy across the rails of said stretch during one and only one step in the cycle of operation of said relays during which the contacts of at least one of said transmitter relays are picked up.

'1. In a coded railway signaling system, in combination, a stretch of railway track through which trafiic may move in either direction, a code following track relay at each end of the stretch governed by coded energy supplied over the rails of the stretch, code detecting means associated with each track relay and responsive to operatween a first and a second position at a selected rate, a first and a second transmitter relay each having contacts movable between a released and a picked-up position, a pick-up circuit for said first transmitter relay including a back contact of the associated track relay and a first position contact of the associated code transmitter, a stick circuit for said first transmitter relay including a back contact of the associated track relay and a second position contact of the associated code transmitter, a pick-up circuit for said second transmitter relay including a back contact of the associated track relay and a front contact 0! the associated first transmitter relay and a second position contact of the associated code transmitter, and a stick circuit for said second transmitter relay including a first position contact of said code transmitter, and a circuit including a front contact of said second transmitter relay for connecting a source of energy across the rails of said stretch.

8, In a coded railway signaling system, in combination, a stretch of railway track through which trafiic may move in either direction, a code following track relay at each end of the stretch governed by coded energy supplied over the rails of the stretch, code detecting means associated with each track relay and responsive to operation thereof, a signal at each end of the track stretch governed by the associated code detecting means, and code generating means at each end of the stretch for supplying impulses of energy to the rails of the stretch, each of said code generating means comprising a code transmitter having contacts which are continuously operated between a first and a second position ata selected rate, a first and a second transmitter relay each having contacts movable between a first and a second position, each track relay governing the associated transmitter relays so that the transmitter relay contacts occupy their first position when the tracl: relay is picked up, a circuit including a bacl; contact of the associated track relay and a first position contact of the associated code transmitter for operating the contacts of the first transmitter relay from their first to their second position, a circuit'including a back contact of the associated track relay and second position contacts of the associated first transmitter relay and of the associated code transmitter for operating the contacts of the second transmitter relay from their first to their second position, means responsive to continued operation of said code transmitter subsequent to movement of the contacts of the associated second transmitter relay to their second position for causing the contacts of the associated first and second transmitter relays to occupy their first position, and a circuit including a second position contact of said second transmitter relay for connecting a source of energy across the rails of said stretch.

9. In a coded railway signaling system, in combination, a stretch of railway track through which trafiic may move in either direction, a code following track relay at each end of the stretch governed by coded energy supplied over the rails of the stretch, code detecting means associated with each track relay and responsive to operation thereof, a signal at each end of the track stretch governed by the associated code detecting means, and code generating means at each end of the stretch for supplying impulses of energy to the rails of the stretch, each of said code generating means comprising a code transmitter having contacts which are continuously operated between a first and a second position at a selected rate, a first and a second transmitter relay each having contacts movable between a released and a picked-up position, each track relay governing the associated transmitter relays so that the transmitter relays are released when the track relay is picked up, control means for each first transmitter relay for at times supplying energy thereto when the associated track relay is released and the contacts of the associated code transmitter are in their first position and for thereafter maintaining the supply of energy to said first transmitter relay until a movement of the code transmitter contacts subsequent to picking up of the contacts of the associated second transmitter relay, control means for each second transmittter relay for supplying energy thereto on movement of the contacts of the associated code transmitter to their second position when the associated track relay is released and the" as 32 sociated first transmitter relay is energized and for thereafter maintaining the supply of energy to said second transmitter relay until a movement of the contacts of the associated code transmitter subsequent to release of the assoclatedfirst transmitter relay, and circuits governed by said first and second transmitting relays for at times effectivel connecting the associated track relay and at other times connecting a source of energy across the rails of the stretch, the circuits governed by the transmitter relays at each end of the stretch being arranged so that the associated track relay is connected across the rails of the stretch when the contacts of both of the transmitter relays at that end of the stretch are released and so that the associated source of energy is connected across the rails of the stretch only when the contacts of said second transmitter relay at that end of the stretch are picked up. 10. In a coded railway signaling system for a section of railway track having a code following track relay responsive to impulses of energy supplied over the rails of said section, code generating means for supplying said impulses of energy to the rails of said section, said code generating means comprising a code transmitter having contacts which are continuously actuated between a first and a second position, a series of transmitter relays each having contacts movable betweena released and a picked-up position, pickup circuits for sequentially energizing said transmitter relays in order, one for each movement of the contacts of said code transmitter, stick circuits for holding said transmitter relays energized until all of said transmitter relays are energized and for thereafter sequentially deenergizing said transmitter relays in order, one for each movement of the contacts of said code transmitter, and a circuit governed by said transmitter relays for connecting a source of energy across the rails of said stretch during one and only one step in each cycle of operation of said transmitter relays.

'11. In a coded railway signaling system for a section of railway track having a code following track relay responsive to impulses of energy supplied over the rails of said section, code generating means for supplying said impulses of energy to the rails of said section, said code generating means comprising a code transmitter having contacts which are continuously actuated between a first and a second position, a first, a second.

and a third transmitter relay each having contacts movable between a released and a pickedup position, pick-up circuits for sequentially energizing said transmitter relays in order, one for each movement of the contacts of said code transmitter, stick circuits for holding said transmitter relays energized until all of said transmitter relays are energized and for thereafter sequentially deenergizing said transmitter relays in order, one for each movement of the contacts of said code transmitter, and a circuit eflectlve only when said second transmitter relay is energized and said thirdtransmitter relay is deenergized for connecting a source of energy across the rails of said section.

12. In a coded railway signaling system for a section of railway track having a code following track relay responsive to impulses of energy sup plied over the rails of said section, code generating means for supplying said impulses of energy to the rails of said section, said code generating means comprising a code transmitter having contacts which are continuously actuated between a s 33 first and a second position, a first, a second an a third transmitter relay each having contacts movable between a first and a second position, control circuits for sequentially operating the transmitter relays in order to cause their contacts to move .from their first to their second position, one relay being operated for each movement of the contacts of said code transmitter until all of said transmitter relays have had their contacts operated to their second position and for thereafter sequentially operating the transmitter relays in order to cause their contacts to move from their second to their first position, one relay being operated for each movement of the contacts of said code transmitter until all of said transmitter relays have had their contacts operated to their first position, and a circuit 7 effective only when the contacts of said second transmitter relay are in their second position and the contacts of said third transmitter relay are in their first position for connecting a source of energy across the rails of said section.

13. In a coded railway signaling system, in combination, a stretch of railway track through which trafllc may move in either direction, a code .following track relay at each end of the stretch governed by coded energy supplied-over the rails of the stretch, code detecting means associated with each track relay and responsive to operation thereof, a signal at each end of the track stretch governed by the associated code detecting means, and code generating means at each end of the stretch for supplying impulses of energy to the rails of the stretch, each of said code generating means comprising a code transmitter having contacts which are continuously operated between a first and a second position at a selected rate, a series of transmitter relays each having contacts movable between a released and a picked-up position, pick-up circuits including a back contact of the track relay at an end of the stretch for sequentially energizing the associated transmitter relays in order, one for each movement of the contacts of the associated code transmitter, stick circuits including a back contact of the track relay at an end of the stretch for holding the associated transmitter relays energized until all of said transmitter relays are energized and for thereafter sequentially deenergizing said transmitter relays in order, one for each mover ment of the contacts of the associated code transmitter, and a circuit governed by said transmitter relays for connecting a source of energy across the rails of the stretch when the contacts of the second transmitter relay are picked up and the contacts of the third transmitter relay are released.

14. In a coded railway signaling system, in combination, a stretch of railway track through which traflic may move in either direction, a code following track relay at each end of the stretch governed by coded energy supplied over the rails of the stretch, code detecting means associated with each track relay and responsiv to operation thereof, a signal at each end of the track stretch governed by the associated code detecting means, and code generating means at each end of the stretch for supplying impulses of energy to the rails of the stretch, each of said code generating means comprising a code transmitter having contacts which are continuously operated between a first and a second position at a selected rate, a series of transmitter relays each having contacts movable between a released and a picked-up position, pick-up circuits including a back contact of the track relay at an end of the stretch for sequentially energizing the associated transmitter relays in order, one for each movement of the contacts of the associated code transmitter, stick circuits including a back contact of the track relay at an end of the stretch for holding the associated transmitter relays energized until all of said transmitter relays are energized and for thereafter sequentially deenergizing said transmitter relays in order, one for each movement of the contacts of the associated code transmitter, means governed by said transmitter relays for connecting a source of energy across the rails of the stretch durin a step in the cycle of operation of said transmitter relays in which more than one of the transmitter relays is energized, means for connecting the rails of the stretch together in the step in the cycle of operation of the transmitter relays succeeding the step during which the source of energy is connected across the rails of the stretch, and means for connecting the track relay across the rails of the stretch during the remaining steps in the cycle of operation of the transmitter relays.

15. In a coded railway signaling system, in combination, a stretch of railway track through which trafllc may move in either direction, a code following track relay at each end of the stretch governed by coded energy supplied over the rails of the stretch, code detecting means associated with each track relay and responsive to operation thereof, a signal at each end of the track stretch governed by the associated code detecting means, and code generating means at each end of the stretch for supplying impulses of energy to the rails of the stretch, each of said code generating means comprising a code transmitter having contacts which are continuously operated between a first and a second position at a selected rate, a first, a second and a third transmitter relay each having contacts movable between a released and a picked-up position, pick-up circuits including a back contact of the track relay at an end of the stretch for sequentially energizing the associated transmitter relays in order, one for eachmovement of the contacts of the associated code transmitter, stick circuits including a back contact of the track relay at an, end of the stretch for holding the associated transmitter relays energized until all of said transmitter relays are energized and for thereafter sequentially deenergizing said transmitter relays in order, one for each movement of the contacts of the associated code transmitter, means governed by said transmitterrelays for connecting a source of energy across the rails of said stretch during a step in the cycle of operation of said transmitter relays in which more than one of said transmitter relays is energized, and means governed by said transmitter relays for connecting the associated track relay across the rails of said stretch during a plurality of the remaining steps in the cycle of operation of said transmitter relays.

16. In a coded railway signaling system, in combination, a stretch of railway track through which trafllc may move in either direction, a code following track relay at each end of the stretch governed by coded energy supplied over the "rails of the stretch, code detecting means associated with each track relay and responsive to operation thereof, a signal at each end of the track stretch governed by the associated code each end of the stretch for supplyin impulses 

